Louis Trevelyan, rich, handsome and intelligent, marries Emily, the beautiful and spirited daughter of the Governor of the Mandarin Islands. Perfectly matched, the Trevelyans seem to be the epitome of comfortable upper middle-class Victorian values, until the mischievous Colonel Osborne appears. He Knew He Was Right describes the failure of a marriage caused by the unreasonable jealousy of a husband exacerbated by the stubbornness of a willful wife.